Changing the subject for a moment...I paid a visit to our local stove store this morning and came home with a massive piece of ceramic glass ! It was damaged in transit, destined as a new installation in a hotel, it had to be replaced but it only has a small chip in one corner. It must be around 100cm x 60cm.
I can’t find a method to re stack fuel without smoking up the glass and over fueling.
I just accidentally discovered that if you reload the stove before the start of the coaling phase and only use one or two large pieces of wood then there is no sooting up of the glass or overfueling. The fire just seems to carry on as if nothing's changed.
I can’t find a method to re stack fuel without smoking up the glass and over fueling.
I just accidentally discovered that if you reload the stove before the start of the coaling phase and only use one or two large pieces of wood then there is no sooting up of the glass or overfueling. The fire just seems to carry on as if nothing's changed.
same deal with the riserless core oven , once there's room add another log.
The Vermiculite board shelf sits on top of the sides of the afterburner so is a bit larger: 280mm x 360mm x 50mm
Afterbunner port (gap glass/shelf): 80x230 = 18400mm2 =104%CSA, or better 110x230??
The gap between the inside of the glass and the front edge of the shelf should be 110mm x 230mm.
Top chamber (whole lenght): 63x275 (100% CSA), lenght 458mm Exit/End port 120x145 (=100%CSA) (on side, top or back)
The total length from the inside of the glass to the rear of the top chamber is 470mm Total length from the front edge of the shelf to the rear of the top chamber is 360mm
At the end of last season I was experimenting with a 1 CSA top chamber (page 56), I wasn't happy with the double vortex on it so expanded it to 105% and reduced the exit port back to 80% CSA and turned the vermiculite board around so all the pieces have the wrinkly side out. This setup seemed to work very well, and also works well with half loads: www.vftshop.com/images/others/Stove/topchamber100-80.JPG (It's sooty because I have been burning paper rubbish in the stove over summer).
Air inlet 20%CSA
The primary air should be 20% CSA. Works best when diffused over a larger area at the bottom of the door than all one spot blowing on the fire: donkey32.proboards.com/post/35803/thread
120mm system -> 60x60x3.142=11311csa (64% CSA) for retangular area scale: x0.80 (for 125mm -> x0.833 ;for 130mm x0.85; for 100mm x 0.66)) firebox: 244x244x336 (59536csa = 64% CSA) → volume: 20lt = 51% of 39lt so ...could be volume = 64% = 25lt→ 244x244x420 ??
I have never tried a larger volume firebox like that so dont know how it would behave. At a guess I'd say it may be prone to overfueling.
Hi Trev, I'm completely new to masonry stoves (probably obvious by the questions) but looking for a better way to heat my cabin than what I'm currently using. Your Vortex stove seems to be the answer so with that out of the way, I have some questions.
1: Your stove is dry stacked for the bell, are there any problems with air infiltration? Would caulking the steel sheets be of any benefit, or even needed?
2: If building the firebox with firebrick rather than casting, would the firebrick be set in mortar, or could it be dry stacked as well?
3: Concerning the steel frame, is it sized to fit tightly with the bricks, or is there some allowance for expansion?
4: I'm working with a 6" chimney and heating 35 m2 with good insulation........will a 6" Vortex run me out of the place?
Thanks in advance, and I hope the imposition is not too great.
Hi Trev, I'm completely new to masonry stoves (probably obvious by the questions) but looking for a better way to heat my cabin than what I'm currently using. Your Vortex stove seems to be the answer so with that out of the way, I have some questions.
Hi Pat, Welcome to the forum.
1: Your stove is dry stacked for the bell, are there any problems with air infiltration? Would caulking the steel sheets be of any benefit, or even needed?
I considered caulking it with high temp silicon, but I really wanted it to be easy to tear down and rebuild if I wanted to make changes, so as the steel joints were very tight fitting with good overlaps I didn't bother and it hasn't been an issue at all. A couple of times at startup in gale force winds I've had blowbacks and the only place it's leaked smoke out was around the door and hot plates, which are the only parts that have sticky fire-rope seals.
2: If building the firebox with firebrick rather than casting, would the firebrick be set in mortar, or could it be dry stacked as well?
The firebox roof would be difficult to make out of firebricks unless you can get some longer than the firebox width/height. Same with the sides if you want to be able to dry stack it. If you mortar it you'll be patching it up every year. If you don't want to cast I would recommend searching for some firebrick slabs that you can cut to size. There's no complicated shapes in it now so casting it is a lot easier than it was. I can cast the whole firebox now just with one mould the size of the side pieces. For the roof and base you just cut a few offcuts of wood to sit in the mould to make the smaller sized pieces. The slopped floor can be cut out of a side piece cast: www.vftshop.com/images/others/Stove/V-floor2.jpg
3: Concerning the steel frame, is it sized to fit tightly with the bricks, or is there some allowance for expansion?
I allowed a few millimeters for expansion, roughly 1mm for every 200mm. The overlaps of the frame cover the gaps for this. The only place I had problems from thermal expansion was the front steel sheet, it would bow out a little in the middle causing the door to drag on the hearth. To solve it I put a threaded bar through the stove: donkey32.proboards.com/post/33592/thread
4: I'm working with a 6" chimney and heating 35 m2 with good insulation........will a 6" Vortex run me out of the place?
A 5" would probably be OK unless you are somewhere with very cold winters. I'm in Ireland in a 42 m2 cabin with fair insulation, and I was considering reducing it to a 5", but the top chamber setup I was experimenting with at the end of last season worked well with half loads so I may stick with the 6" now.
Thanks in advance, and I hope the imposition is not too great.
This year I decided to try adapting the design to make a dedicated 4" cookstove. We often get people coming to the forum asking for small cooking stove designs for the 3rd world, and I've been wondering how well this would work.
To adapt it to a dedicated cookstove I wanted the hotplate above the port, as the main difficulty I see with getting heat into hotplates is the problem of laminar flow, where a layer of air separates the flame from the metal plate.
I removed the top chamber and cut some small pieces of vermiculite board to make the side and back walls of the afterburner. The top is now the hotplate and the exit of the afterburner is to the right and left sides (65mm wide x 75mm high). The chimney was the same as previous.
The increased resistance of the double exit channels seemed to have the same effect I observed on my 6" stove when I increased the surface area to volume ratio for the top chamber (Page 56).
The little cookstove ran excellent, the vortex stayed doggedly in the afterburner the whole burn. The fire ran for over an hour on the kindling I'd usually use to light the 6 incher. I boiled several large kettles of water on the cooktop while it was running.
This is fantastic, Trev! I’ve been following along and trying to find a solution which would put the hottest zone of a cooking plate at the center, with decreasing temps outward toward the edges… your idea of splitting the afterburner into 2 parts —basically making it a sideways contraflow— is simply brilliant.
I’d love to see how this performs if the rear exit were diverted back downward into a thermal battery of more mass, before being routed back upward again to the chimney. I think I’ll use your design here as the a jumping-off point to try just that. Thank you so much for sharing all this info and experimentation.
This year I decided to try adapting the design to make a dedicated 4" cookstove. We often get people coming to the forum asking for small cooking stove designs for the 3rd world, and I've been wondering how well this would work.
To adapt it to a dedicated cookstove I wanted the hotplate above the port
I’m curious how this test model is getting its secondary air… is it just drawing in through the tiny gaps between dry-stacked blocks?
I see the primary air is from the bottom of the “door” — that gap between glass and floor provided by the spacers to the left and right.
Thanks again, and cheers.
The accuracy of info we share here is more important than my ego, your ego, or Peter's ego. None of us has exclusive ownership over the truth.
Thanks Forsythe, So long as it's well constructed without leaks and has a proper door and full length chimney it will work just as well on a contraflow mass. If I was building the model from scratch today I would use a lot less mass in the firebox walls, it is too much for such a small stove.
The model is not dry stacked, there is a thin clay slip mortar. It gets its primary and secondary air from around the glass firebox 'door'. The glass is propped up so there is a 20mm gap along the bottom front (primary), and is angled out at the bottom so there is a 20mm gap either side which gets narrower as it goes up to nothing at the top (secondary). The important thing seems to be that the air is well mixed into the smoke and gases in the firebox, a long thin gap is better at mixing the incoming air than one large square or circle.
If I was building the model from scratch today I would use a lot less mass in the firebox walls, it is too much for such a small stove.
Ah, good to know. I guess the advantages of the thermal “flywheel” being able to gasify additional reloads of wood (simply from the residual heat in all that firebox mass) was outweighed by the time it took to get the mass hot enough to burn cleanly?
For something like a cook stove being used for very long cycles of multiple re-loads, the extra mass might be useful. (If one were able to close down the air and keep that “sweet-spot” of gasifying in the firebox and combustion in the afterburner. The use-case I’m thinking of here would be for something like 8-10 hour continuous low-burns (after the firebox mass was sufficiently charged.) Fireboxes capable of giving that heat back for a long gasification state seem to be able to run well so long as they’re kept refueled (the Pyroclassic seems to operate on this principle, for example, and I think you mentioned your stove doing that somewhere around pg 27-30.)
It gets its primary and secondary air from around the glass firebox 'door'. The glass is propped up so there is a 20mm gap along the bottom front (primary), and is angled out at the bottom so there is a 20mm gap either side which gets narrower as it goes up to nothing at the top (secondary). The important thing seems to be that the air is well mixed into the smoke and gases in the firebox, a long thin gap is better at mixing the incoming air than one large square or circle.
Trev
Ah, yes, I see. This makes a lot of sense in terms of preventing laminar flow along the firebox walls and/or the secondary air tubes/ ports/ manifolds, etc. and getting a thorough mixing with turbulent flow. (I also noted your mention of how injected air just before the port tends to disrupt the ram’s horns formation in the afterburner.)
I read that post where you described making the door with a 2mm gap all around so it doesn’t seal air-tight, and I wondered: Does this mean abandoning the “Austrian method” of shutting down air and stopping the coaling phase (to then burn that leftover charcoal in the beginning of the next run)? …I’m just trying to imagine how that Austrian method would work with the door intentionally designed not to seal air-tight.
I’m also curious how necessary the ash-box below the firebox would be. On the one hand, it would make continuously reloading-while-hot easier, (as the ash wouldn’t build up as much on the firebox floor. —But on the other hand: the air coming in through the ash box floor seemed to create the high CO numbers mentioned a while back… and… metal grates in firebox floors tend to be sacrificial parts which need periodic replacement.)
If you were building from scratch today, would you include that ash-box or forego it?
Thanks again for taking the time to help out us learners and beginners. Forsythe
Last Edit: Jul 25, 2021 19:39:02 GMT -8 by Forsythe
The accuracy of info we share here is more important than my ego, your ego, or Peter's ego. None of us has exclusive ownership over the truth.
The 6" stove has 2" thick insulated firebox walls, the 4" has 4-1/2" uninsulated walls, so if you scale that up it's like having 7"+ thick walls on the 6" stove! Fine if you're running the stove all day with lots of reloads but makes for very slow startups if not. First burn in this new cookstove setup didn't even change the temp of the outside of the firebox. 1-1/2" firebox walls with insulation on the outside ought to be plenty on a 4".
I didn't have a lot of success using the Austrian method, the strong winds here mean that even with the best stove door seals you can have, it still managed to suck enough air through to keep the embers smoldering.
I've found for me a better method is to add a little bit of bottom air up through the coals in the latter part of the burn, this keeps flame in the afterburner longer, extending the flame phase, burning off more CO. from the embers and shortening the coaling phase. The bottom air only increased the CO. when opened to early or too much.
This works better for me as I prefer to have the fire completely burnt out to white ash, then fully close the chimney damper to stop the heat being sucked out of the mass by the wind overnight. The ashtrap only needs a slit half an inch wide above the ashbox, this doesn't require any metal in the firebox. I wouldn't be without the ashbox now, not having to shovel ashes out really cuts down the amount of dust in the house.
I'm slowly gathering materials to build a 4" Vortex stove. The following is the plan I have in mind and I'd appreciate your critique.
The firebox will be dense 1 1/4" firebrick surrounded by 1" vermiculite board. Slightly larger than it's supposed to be: width 9", height 8 3/4", length 12 1/4". I'm hoping I can use 1 1/2" vermiculite as the firebox roof and throat, reading through the thread seems to suggest it might be okay there. After seeing the results of your 4" project stove, I think the thinner firebrick will retain enough heat to carry things through.
The afterburner will be built with 1" vermiculite which is obtainable at a fraction of the cost of other insulating materials such as ceramic fiber. I can also get 2600oF insulating blanket for the firebox, but I had hoped to use the vermiculite to help support the firebricks.
The mass will be concrete brick as firebrick is ridiculously priced @ $8.00 CDN each and even at that price, there are none to be found here. I thought to use firebrick as the top layers to take the brunt of the heat. Or possibly a homemade refractory mix. I have the ingredients for a mix, though I doubt it's usefulness for anything like a firebox. But it may work okay in the mass as it should be out of the worst of the flame.
I have a 6" insulated chimney now and I'm unsure as to what size the internal chimney should be. I'm concerned that a 4" chimney may choke the stove, but a 6" may rob the mass of the heat much faster. Considering that the mass will be somewhat smaller than in a 6" system.
I'm kicking around the idea of building a steel frame for the firebox and adding tabs to use for mounting the door frame. The steel would be around the vermiculite, so well away from flame. This is because I fear mounting the frame to the masonry will cause problems......stripped holes, cracked masonry, etc:. And also to give support to the firebox, basically make it a solid unit. It might work to stop any bowing of the front steel panel as well. Then again, it will also make replacing bricks kinda hard without removing the entire firebox.....maybe not a great idea.
I've chosen the 4" stove because I think (okay, hope) it will heat my small cabin even if 2 fires a day, and it's doable using firebricks for the firebox. Though, when we hit -35C here, there might be a wake up call for me. For a bigger stove, castable refractory is nonexistent here as is any knowledge of such things......I get a lot of blank looks and suggestions to use furnace cement or just use a steel box stove. Bringing materials in means shipping for up to 500 kilometers, so is avoided.
Does any of this rambling look like it might have a remote chance of working? It's not like I know what I'm doing as I've never built anything like this.
I must of missed the bit about where you live but it must be remote! I will let Trev answer you tech questions but standard concrete block is not the best choice for mass as it contains far to much air. You might be able to get high compression blocks that are in effect vibrated concrete blocks but if brick is out of the question then maybe you can use wood shuttering and poured concrete .
Martyn is right about the concrete idea. Do people use electric storage heaters where you are? They contain the magnetite bricks I used as the main mass in my stove, they're excellent for storing heat. Alternatively old floor/wall tiles work so long as they're the kiln fired type, not as dense as firebrick but a lot better than concrete blocks.
For the castable, is calcium aluminate cement (AKA fondue cement) available there? If you can get that then you can make a grog by smashing up old ceramics, anything that's fired at a high temperature, then screen it through a 3mm sieve. Porcelain and old red bricks seems to be what they use to make the commercial product sold here, as I've had some bags with chunks that have escaped the crusher. A mix of 4 grog to 1 CA cement works really well. We used it and crushed old French clay roof tiles to make a load of cast slabs in 2 stoves that have been running for 6+ years now, some of the pieces are even in the secondary burn chamber and all are still doing fine.
The 1 1/2" vermiculite should be OK for the firebox roof and port. Only problem I've had with vermiculite board is when I used it outside for experiments and it got rained on and was damp, then the larger pieces cracked.
For your chimney worries, you could have a 5" internal so it transitions more gradually from 6" to 5" to 4", or you could fit and old style chimney damper in the 6". I have one where the stove connects to the 6" chimney. I'm on the Atlantic coast so it's useful to slow the draw down in strong winds. I also use it to close off the mass when all the embers are completely burnt out.
I'm still delighted with the steel exterior frame on mine, it makes it so much easier for changes/repairs/cleaning etc. I can remove my firebox casts by removing the door & door frame, (which is held in by 4 bolts into the outer frame).
A 5" might be better if you get temperatures like -35C. I was thinking to scale mine down to a 5", but now with the latest top chamber developments the stove seems to burn just as well on half loads, so that gives more flexibility.
fierolepou: Hi everybody! Starting a project from scratch, this is a goldmine!
Dec 10, 2022 5:20:09 GMT -8
Solomon: Best way to not die in a house fire is to build a stove where the really hot stuff isn't near the flammable stuff.
Jan 10, 2023 11:34:39 GMT -8
beppe: Hi to everybpdy. I'm new about the rocket stoves and this forum
Aug 30, 2023 22:17:32 GMT -8
beppe: I have a living room+ kitchen of 75 square meters that was heated by an ordinary pellet stove with a power of 8KW.
Aug 30, 2023 22:19:29 GMT -8
beppe: I want to switch to a DIY pellet rocket stove but I haven't found yet a project that is really suitable for my situation. Is there anybody able to indicate to me a good detailed project?
Sept 4, 2023 9:05:15 GMT -8
sksshel: Yes, very happy with my DSR2. I had not heard about the DSR3. I probably won't be using it but I will look into it.
Oct 16, 2023 9:15:37 GMT -8
rockinon: I have some questions about a Rocket Mass Heater, as I am in progress of getting a place built in Arkansas in the mountains of NW Arkansas and it will be very helpful. How can I add pictures to illustrate what I am requesting
Jan 23, 2024 11:01:07 GMT -8
dd24: Bonjour, Quelqu'un expérimente t-il sur les poêles "bubafonya" ou "stopuva"? merci pour votre réponse!
Mar 2, 2024 10:32:32 GMT -8
marcios: Hi Trev, What dimensions did you keep for the top chamber?
May 9, 2024 13:41:47 GMT -8
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Donkey: rockinon, place them on some other web hosting service and link them here.
Jun 27, 2024 16:25:24 GMT -8
atrii: How can I see these photos Donkey?
Jul 16, 2024 16:17:59 GMT -8
Donkey: atrii When the images are properly linked, they will be visible.
Jul 21, 2024 19:02:47 GMT -8
dvawolk: For images i use "Greenshot" app - i can print screen part or whole of my screen and upload them directly to imgur throught the context menu. Works very well and fast for me...
Aug 21, 2024 2:21:17 GMT -8
martinm: Hi there , looking for info on hot water heat exchanger for integrating in the bell of masonry rocket stove.
Sept 10, 2024 3:43:38 GMT -8
lightworker: Hi beppe:
Oct 19, 2024 16:45:02 GMT -8
